1. Field of the Invention
The present invention relates generally to the field of assisted walking for the rehabilitation of handicapped persons, and more particularly, to a knee-ankle-foot orthotic device designed to enable safe ambulation in patients suffering from weakness or lack of control of the knee joint.
2. Description of the Related Art
Orthotic devices are often provided for patients afflicted with polio, spinal cord injury, cerebrovascular accidents (e.g., stroke) and multiple sclerosis. In addition, patients suffering from nerve root injuries, other neurological or muscular diseases, or who experience secondary loss of control of the knee may require the use of an orthotic device. The problem that these orthotic devices attempt to address is the lack of knee control during the weight-bearing stages of the gait cycle.
Numerous attempts for enabling patients a safe ambulation have been provided, though none with the functionality of the present invention. For example, the UTX® Swing Knee Ankle Foot Orthosis manufactured by Becker Orthopedic of Troy, Mich., is a device intended to stabilize the knee during the stance phase of gait but enable knee flexion during the swing phase. At the end of the swing phase, as the knee reaches full extension, a ratchet engages to stabilize the knee. At the end of the stance phase, as the ankle dorsiflexes, a cable linkage is used to unlock the knee joint and allow it to move freely.
The Free-Walk design manufactured by Otto Bock of Duderstadt, Germany and Minneapolis, Minn. creates a natural gait cycle by locking during the stance phase and unlocking during the swing phase. The automatic lock is initiated by knee extension and is only released to swing freely when a knee extension moment occurs simultaneously with ankle dorsiflexion in the terminal stance.
The Swing Phase Lock (SPL) manufactured by BASKO of Amsterdam, Netherlands is yet another existing knee hinge orthosis system. This system automatically unlocks in order to allow knee flexion, and it locks before heel contact takes place. The SPL hinge system can only unlock when there is no flexion moment or strain of bending put on the hinge.
U.S. Pat. No. 4,632,096 (Harris, 1986) is an example of a prior art orthotic system for the leg. This system releases automatically upon a pre-selected dorsiflexion of the ankle followed by a pre-selected flexion of the ankle. The orthotic devices provided with a lock hinge that spans the pivoting means and locks the upper member and lower member when the leg approaches extension during a gait cycle.
Examples of other prior art knee braces and/or orthotic joints include U.S. Pat. Nos. 6,960,175 (Myers, 2005); 6,770,045 (Naft et al., 2004); U.S. Pat. No. 6,635,024 (Hatton et al., 2003); U.S. Pat. No. 6,517,503 (Naft et al., 2003); U.S. Pat. No. 6,159,248 (Grammas, 2000); U.S. Pat. No. 5,899,869 (Barrack, Jr., et al., 1999); U.S. Pat. No. 5,776,086 (Pansiera, 1998); U.S. Pat. No. 4,451,939 (Thompson, 1984); U.S. Pat. No. 2,943,622 (Nelson, 1960); U.S. Patent Application Pub. No. 20060211966 (Hatton et al.); U.S. Patent Application Pub. No. 2004/0049291 (Deharde et al.); U.S. Patent Application Pub. No. 2002/0183673 (Naft et al.); and U.S. Patent Application No. 20020269402 (Hatton et al.).
In contrast to prior art devices, the present invention utilizes a low-profile cabling system that will automatically unlock at terminal stance, to allow for free knee flexion, and then reengage at mid-swing, permitting only knee extension (and not knee flexion). This feature ensures knee joint stability prior to heel contact and provides added safety, security and stability for individuals who fail to reach full knee extension.